My_Jobs的专栏

题目1：给出一个数据流，这个数据流的长度很大或者未知。并且对该数据流中数据只能访问一次。请写出一个随机选择算法，使得数据流中所有数据被选中的概率相等。对于复杂问题一定要学会归纳总结，即从小例子入手，然后分析，得出结论，然后在证明。不然遇到一个抽象问题，不举例感觉这个问题，直接解还是比较难的。对于此问题的难处就是数据流的长度未知，如果已知，so easy。现在进行归纳总结：1）

Given a complete binary tree, count the number of nodes.Definition of a complete binary tree from Wikipedia:In a complete binary tree every level, except possibly the last, is completely filled,

两道题放一块了，一个是判断两棵树是否相同：Given two binary trees, write a function to check if they are equal or not.Two binary trees are considered equal if they are structurally identical and the nodes have

Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times. The algorithm should run in linear time and in O(1) space.此题是Majority Element的继续，关于此题可以移步至Majority Elem

Given s1, s2, s3, find whether s3 is formed by the interleaving of s1 and s2.For example,Given:s1 = "aabcc",s2 = "dbbca",When s3 = "aadbbcbcac", return true.When s3 = "aadbbbaccc", ret

Given a string S and a string T, count the number of distinct subsequences of T in S.A subsequence of a string is a new string which is formed from the original string by deleting some (can be non

Implement the following operations of a stack using queues.push(x) -- Push element x onto stack.pop() -- Removes the element on top of the stack.top() -- Get the top element.empty() -- Return whet

Implement the following operations of a queue using stacks.push(x) -- Push element x to the back of queue.pop() -- Removes the element from in front of queue.peek() -- Get the front element.empt

Write a program to check whether a given number is an ugly number.Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 6, 8 are ugly while 14 is not ugly si

Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.For example, given the following triangle[ [2], [3,4], [

Given a 2D binary matrix filled with 0's and 1's, find the largest square containing all 1's and return its area.For example, given the following matrix:1 0 1 0 01 0 1 1 11 1 1 1 11 0 0 1 0

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.push(x) -- Push element x onto stack.pop() -- Removes the element on top of the stack.top() -- Get

Given two words word1 and word2, find the minimum number of steps required to convert word1 to word2. (each operation is counted as 1 step.)You have the following 3 operations permitted on a word:

A message containing letters from A-Z is being encoded to numbers using the following mapping:'A' -> 1'B' -> 2...'Z' -> 26Given an encoded message containing digits, determine the total nu

Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].Solve it without division and in O

此处的三个题跟Maximum Subarray，可以先看此题I)Say you have an array for which the ith element is the price of a given stock on day i.If you were only permitted to complete at most one transaction (ie, b

Find the contiguous subarray within an array (containing at least one number) which has the largest sum.For example, given the array [−2,1,−3,4,−1,2,1,−5,4],the contiguous subarray [4,−1,2,1] ha

iven a binary tree, find its maximum/minimum depth.The maximum/minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.两个很相似的题，但是解法完全不怎么

Given an array where elements are sorted in ascending order, convert it to a height balanced BST.没什么可说的，直接上代码：

Given a binary tree, determine if it is a valid binary search tree (BST).Assume a BST is defined as follows:The left subtree of a node contains only nodes with keys less than the node's key.Th

The gray code is a binary numeral system where two successive values differ in only one bit.Given a non-negative integer n representing the total number of bits in the code, print the sequence of

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.For example, given n = 3, a solution set is:"((()))", "(()())", "(())()", "()(())", "()()

问题：有一个100层高的楼，如果一个鸡蛋从n层掉下来或者n层以上，鸡蛋就会碎掉。已知，现在有两个鸡蛋，找到满足条件的n，使在最坏情况下，丢鸡蛋的次数最少。原题链接可以转到wiki：点击打开链接很明显，不管egg1怎么丢，egg2肯定得线性得丢。我们假设egg1每次丢10层，即按10f, 20f, 30f, 40f, 50f, 60f, 70f, 80f, 90f, 100f。则，如

三种不同的方式，生产一个集合的所有子集，回溯法、迭代法。。。

有一类题是位操作，但是感觉在面试中，很少有这种题，毕竟不需要那么细的操作，感觉位操作在汇编和C语言关系比较大，比较偏底层。但是有时候用位操作往往得到意想不到的效果。http://graphics.stanford.edu/~seander/bithacks.html关于常见的为操作可以看这链接，将了好多方法，现将比较常见的整理一下。一、位的基本操作基本操作主要有六种，与、或、异或、

题目：Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.You may assume that the array is non-empty and the majority

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two node

I)Given an array of integers, every element appears twice except for one. Find that single one.Note:Your algorithm should have a linear runtime complexity. Could you implement it without usi

Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.Note:Elements in a triplet (a,b,c

输入一颗二叉搜索树，将该二叉搜索树转换成一个排序的双向两步。空间复杂度为O(1).最笨的方法就是中序遍历放在一个数组或链表中，再次遍历串联起来。但是要求空间复杂度为O(1)，就没办法这么做了，这时候可以参考这个解法。http://blog.youkuaiyun.com/my_jobs/article/details/47666909判断一个树是不是一颗二叉搜索树，可以模仿最后的那个方法。本题跟

题目：Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.For example:Given the below binary tree

Given a binary tree struct TreeLinkNode { TreeLinkNode *left; TreeLinkNode *right; TreeLinkNode *next; }Populate each next pointer to point to its next right node.

Given a binary tree, determine if it is height-balanced.For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never diffe

Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).For example:Given binary tree {3,9,20,#,#,15,7}, 3 / \ 9 20

Given a binary tree, flatten it to a linked list in-place.For example,Given 1 / \ 2 5 / \ \ 3 4 6The flattened tree should look like: 1

Given an integer n, count the total number of digit 1 appearing in all non-negative integers less than or equal to n.For example:Given n = 13,Return 6, because digit 1 occurred in the followin

The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other.Given an integer n, return all distinct solutions to the n-queens puzzle.

Given a string s and a dictionary of words dict, determine if s can be segmented into a space-separated sequence of one or more dictionary words.For example, givens = "leetcode",dict = ["leet"

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.跟题目http://blog.youkuaiyun.com/my_jobs/article/details/431

The count-and-say sequence is the sequence of integers beginning as follows:1, 11, 21, 1211, 111221, ...1 is read off as "one 1" or 11.11 is read off as "two 1s" or 21.21 is read off as